:root {
  --color-surface: #fdfdfd;
  --color-surface-alt: #f3f3f3;
  --color-surface-deep: #e5e5e5;
  --color-ink: #393233;
  --color-ink-soft: #685e60;
  --color-ink-muted: #857a7c;
  --color-line: #dad8d9;
  --color-primary: #e01f39;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #f9dee2;
  --color-accent: #e31c36;
  --color-accent-ink: #ffffff;
  --color-highlight: #f8d4d9;
  --color-focus: #e20e2a;
  --color-contrast-surface: #1f1012;
  --color-contrast-ink: #e7e4e5;
  --color-contrast-line: #4b3f40;
  --color-contrast-accent: #e73b52;
  --overlay-scrim: linear-gradient(180deg, rgba(31, 16, 18, 0.35) 0%, rgba(31, 16, 18, 0.72) 55%, rgba(31, 16, 18, 0.92) 100%);
  --font-heading: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-body: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --text-xs: 10.1px;
  --text-sm: 14.3px;
  --text-base: 17px;
  --text-lg: 24.0px;
  --text-xl: 34.0px;
  --text-2xl: 48.1px;
  --text-3xl: 68.0px;
  --text-4xl: 96.1px;
  --text-display: clamp(52px, 10.7vw, 137px);
  --text-figure: clamp(44px, 7.7vw, 99px);
  --weight-heading: 898;
  --weight-body: 400;
  --leading-body: 1.65;
  --leading-heading: 1.19;
  --tracking-heading: -0.006em;
  --radius-sm: 0px;
  --radius-md: 0px;
  --radius-lg: 0px;
  --radius-pill: 0px;
  --border-thin: 1px;
  --border-thick: 2px;
  --shadow-1: none;
  --shadow-2: none;
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1240px;
  --measure: 71ch;
  --gutter: 24px;
  --section-y: 105px;
  --section-y-lg: 147px;
}

/* ============================================================
   1. Reset
   ============================================================ */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, h5, h6 {
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

p { margin: 0; }

img {
  display: block;
  max-width: 100%;
  height: auto;
  border: 0;
}

a { color: var(--color-ink); }

button { font: inherit; color: inherit; }

nav ul,
nav ol,
.list-plain {
  list-style: none;
  margin: 0;
  padding: 0;
}

[id] { scroll-margin-top: 104px; }

:focus-visible {
  outline: var(--border-thick) solid var(--color-focus);
  outline-offset: 2px;
}

/* ============================================================
   2. 版式与栅格
   ============================================================ */
.shell {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-4);
}

.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--gutter);
}

.grid > * { grid-column: span 12; }
.grid > .span-3 { grid-column: span 3; }
.grid > .span-4 { grid-column: span 4; }
.grid > .span-5 { grid-column: span 5; }
.grid > .span-6 { grid-column: span 6; }
.grid > .span-7 { grid-column: span 7; }
.grid > .span-8 { grid-column: span 8; }

.section { margin-top: var(--section-y); }
.section--lg { margin-top: var(--section-y-lg); }
.section--tight { margin-top: var(--space-8); }

.display {
  margin: 0;
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 0.9;
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.label {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 400;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.num,
.figure,
.cell-value,
.dtable td,
.dtable th,
.coord-value {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum" 1;
}

.figure {
  margin: 0;
  font-size: var(--text-figure);
  font-weight: var(--weight-heading);
  line-height: 0.9;
  letter-spacing: -0.035em;
  color: var(--color-ink);
}

.figure--primary { color: var(--color-primary); }

.rule {
  height: var(--border-thin);
  background: var(--color-line);
  border: 0;
  margin: var(--space-6) 0;
}

.measure { max-width: var(--measure); }

.stack > * + * { margin-top: var(--space-3); }
.stack--tight > * + * { margin-top: var(--space-1); }
.stack--loose > * + * { margin-top: var(--space-6); }

/* ============================================================
   3. 章节头
   ============================================================ */
.sec-head {
  display: flex;
  align-items: baseline;
  gap: var(--space-3);
  padding-bottom: var(--space-2);
  margin-bottom: var(--space-4);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.sec-num {
  flex: none;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  color: var(--color-ink-muted);
  transition: color 160ms linear;
}

.sec-title {
  margin: 0;
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
}

[data-section] { position: relative; }
[data-section][data-active] .sec-num { color: var(--color-primary); }
[data-section][data-active] > .sec-head {
  border-bottom-color: color-mix(in srgb, var(--color-primary) 38%, var(--color-line));
}

/* ============================================================
   4. 按钮
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 12px var(--space-4);
  border: var(--border-thin) solid var(--color-ink);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-ink);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 700;
  letter-spacing: 0.08em;
  line-height: 1.1;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 140ms linear, color 140ms linear, border-color 140ms linear;
}

.btn:hover {
  background: var(--color-primary-soft);
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.btn--primary {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}

.btn--primary:hover {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-accent-ink);
}

.btn--ghost {
  border-color: var(--color-line);
  color: var(--color-ink-soft);
}

.btn--ghost:hover {
  background: var(--color-surface-alt);
  border-color: var(--color-ink-muted);
  color: var(--color-ink);
}

.btn--on-dark {
  border-color: var(--color-contrast-line);
  color: var(--color-contrast-ink);
}

.btn--on-dark:hover {
  background: var(--color-contrast-accent);
  border-color: var(--color-contrast-accent);
  color: var(--color-primary-ink);
}

/* ============================================================
   5. 面包屑
   ============================================================ */
.breadcrumb {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}

.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-2);
  list-style: none;
  margin: 0;
  padding: 0;
}

.breadcrumb li + li::before {
  content: "/";
  margin-right: var(--space-2);
  color: var(--color-line);
}

.breadcrumb a {
  color: var(--color-ink-soft);
  text-decoration: none;
  border-bottom: var(--border-thin) solid transparent;
}

.breadcrumb a:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.breadcrumb [aria-current="page"] { color: var(--color-ink); }

/* ============================================================
   6. 正文
   ============================================================ */
.prose {
  max-width: var(--measure);
  color: var(--color-ink-soft);
  font-size: var(--text-base);
  line-height: var(--leading-body);
}

.prose p { margin: 0 0 var(--space-3); }
.prose p:last-child { margin-bottom: 0; }

.prose strong { color: var(--color-ink); font-weight: 700; }

.prose a {
  color: var(--color-ink);
  text-decoration: none;
  border-bottom: var(--border-thin) solid var(--color-accent);
}

.prose a:hover { color: var(--color-primary); border-bottom-color: var(--color-primary); }

.pullquote {
  margin: 0;
  padding-left: var(--space-4);
  border-left: var(--border-thick) solid var(--color-primary);
  max-width: var(--measure);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: 700;
  line-height: 1.35;
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.pullquote::before { content: "「"; color: var(--color-primary); }
.pullquote::after { content: "」"; color: var(--color-primary); }

/* ============================================================
   7. 数据单元格 / 数据条
   ============================================================ */
.cell {
  border-top: var(--border-thick) solid var(--color-ink);
  padding-top: var(--space-2);
}

.cell-head {
  display: block;
  margin-bottom: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.cell-value {
  display: block;
  font-size: var(--text-2xl);
  font-weight: 700;
  line-height: 1.02;
  letter-spacing: -0.03em;
  color: var(--color-ink);
}

.cell-value--primary { color: var(--color-primary); }

.cell-note {
  display: block;
  margin-top: var(--space-1);
  font-size: var(--text-sm);
  line-height: 1.5;
  color: var(--color-ink-soft);
}

.bar {
  position: relative;
  width: 100%;
  height: 6px;
  background: var(--color-surface-deep);
}

.bar-fill {
  display: block;
  height: 100%;
  background: color-mix(in srgb, var(--color-ink) 34%, var(--color-surface-deep));
}

.bar-fill--hot { background: var(--color-primary); }

/* ============================================================
   8. 图片容器（展签式）
   ============================================================ */
.media-frame {
  position: relative;
  display: block;
  overflow: hidden;
  background: var(--color-surface-deep);
  border: var(--border-thin) solid var(--color-line);
}

.media-frame img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
  filter: saturate(0.5) contrast(1.06) brightness(0.95);
}

.media-frame--fill { aspect-ratio: 16 / 9; }
.media-frame--square { aspect-ratio: 1 / 1; }
.media-frame--wide { aspect-ratio: 21 / 9; }

.media-frame--fill img,
.media-frame--square img,
.media-frame--wide img { height: 100%; }

.media-scrim {
  position: absolute;
  inset: 0;
  background: var(--overlay-scrim);
  pointer-events: none;
}

.media-caption {
  position: absolute;
  left: 0;
  bottom: 0;
  max-width: 100%;
  margin: 0;
  padding: 6px var(--space-2);
  background: color-mix(in srgb, var(--color-contrast-surface) 90%, transparent);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  line-height: 1.5;
}

/* ============================================================
   9. 表格
   ============================================================ */
.table-scroll {
  width: 100%;
  overflow-x: auto;
  border-top: var(--border-thick) solid var(--color-ink);
}

.dtable {
  width: 100%;
  min-width: 640px;
  border-collapse: collapse;
}

.dtable th,
.dtable td {
  padding: var(--space-2) var(--space-3);
  text-align: left;
  font-size: var(--text-sm);
  line-height: 1.5;
  border-bottom: var(--border-thin) solid var(--color-line);
}

.dtable th {
  font-size: var(--text-xs);
  font-weight: 400;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  white-space: nowrap;
}

.dtable tbody tr { transition: background-color 120ms linear; }
.dtable tbody tr:hover { background: var(--color-highlight); }
.dtable .is-num { text-align: right; }
.dtable td.is-hot { color: var(--color-primary); font-weight: 700; }

/* ============================================================
   10. 时间线 / 步骤 / 标签
   ============================================================ */
.track {
  list-style: none;
  margin: 0;
  padding: 0;
  border-left: var(--border-thin) solid var(--color-line);
}

.track > li {
  position: relative;
  padding: 0 0 var(--space-6) var(--space-4);
}

.track > li:last-child { padding-bottom: 0; }

.track > li::before {
  content: "";
  position: absolute;
  left: -5px;
  top: 7px;
  width: 9px;
  height: 9px;
  background: var(--color-surface);
  border: var(--border-thick) solid var(--color-line);
}

.track > li[data-active]::before { border-color: var(--color-primary); }

.step-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 34px;
  height: 34px;
  padding: 0 var(--space-1);
  background: var(--color-surface-deep);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--color-ink);
}

.tag {
  display: inline-block;
  padding: 3px 8px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  color: var(--color-ink-soft);
  white-space: nowrap;
}

.tag--hot {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.tag--soft {
  background: var(--color-primary-soft);
  border-color: transparent;
  color: var(--color-primary);
}

/* ============================================================
   11. 深色对比区块
   ============================================================ */
.block-dark {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border: 0;
}

.block-dark > .shell {
  padding-top: var(--space-6);
  padding-bottom: var(--space-6);
}

.block-dark h1,
.block-dark h2,
.block-dark h3,
.block-dark .sec-title,
.block-dark .figure,
.block-dark .display { color: var(--color-contrast-ink); }

.block-dark .label,
.block-dark .cell-head { color: var(--color-contrast-accent); }

.block-dark .cell { border-top-color: var(--color-contrast-line); }
.block-dark .cell-note,
.block-dark .prose { color: color-mix(in srgb, var(--color-contrast-ink) 72%, transparent); }

.block-dark .sec-head { border-bottom-color: var(--color-contrast-line); }
.block-dark .rule { background: var(--color-contrast-line); }
.block-dark .dtable th,
.block-dark .dtable td { border-bottom-color: var(--color-contrast-line); color: var(--color-contrast-ink); }
.block-dark .dtable tbody tr:hover { background: color-mix(in srgb, var(--color-contrast-accent) 22%, transparent); }
.block-dark .track { border-left-color: var(--color-contrast-line); }
.block-dark .track > li::before { background: var(--color-contrast-surface); border-color: var(--color-contrast-line); }
.block-dark a { color: var(--color-contrast-ink); }

/* ============================================================
   12. 跳转链接
   ============================================================ */
.skip-link {
  position: absolute;
  left: var(--space-4);
  top: -120px;
  z-index: 200;
  padding: var(--space-2) var(--space-3);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  text-decoration: none;
  transition: top 140ms linear;
}

.skip-link:focus { top: var(--space-2); }

/* ============================================================
   13. 页头
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-surface);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.header-shell {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-4);
  min-height: 84px;
}

.brand-block {
  flex: none;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  text-decoration: none;
  color: var(--color-ink);
}

.brand-mark {
  position: relative;
  flex: none;
  width: 22px;
  height: 22px;
  border: var(--border-thick) solid var(--color-ink);
}

.brand-mark::after {
  content: "";
  position: absolute;
  inset: 4px;
  background: var(--color-primary);
}

.brand-name {
  font-family: var(--font-heading);
  font-size: var(--text-base);
  font-weight: 800;
  letter-spacing: -0.01em;
  line-height: 1.2;
}

.brand-line {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
  padding-left: 30px;
}

.header-rule {
  flex: 1 1 48px;
  min-width: var(--space-4);
  height: var(--border-thin);
  background: var(--color-line);
}

.site-nav { flex: none; }

.nav-list {
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.nav-list a {
  display: inline-block;
  padding: 8px 0;
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  color: var(--color-ink-soft);
  text-decoration: none;
  border-bottom: var(--border-thick) solid transparent;
  transition: color 140ms linear, border-color 140ms linear;
}

.nav-list a:hover { color: var(--color-ink); }

.nav-list a[aria-current="page"] {
  color: var(--color-ink);
  border-bottom-color: var(--color-primary);
}

.header-tools {
  flex: none;
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.coord-index {
  display: flex;
  align-items: baseline;
  gap: var(--space-1);
  margin: 0;
  padding-left: var(--space-3);
  border-left: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
}

.coord-value {
  color: var(--color-primary);
  font-weight: 700;
  letter-spacing: 0.08em;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-2);
  padding: 8px 10px;
  border: var(--border-thin) solid var(--color-ink);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  cursor: pointer;
}

.nav-toggle:hover { border-color: var(--color-primary); color: var(--color-primary); }

.nav-toggle-glyph {
  position: relative;
  display: block;
  width: 16px;
  height: var(--border-thick);
  background: currentColor;
}

.nav-toggle-glyph::before,
.nav-toggle-glyph::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  height: var(--border-thick);
  background: currentColor;
}

.nav-toggle-glyph::before { top: -5px; }
.nav-toggle-glyph::after { top: 5px; }

.read-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -1px;
  height: var(--border-thick);
  overflow: hidden;
}

.read-progress-fill {
  display: block;
  width: 0;
  height: 100%;
  background: var(--color-accent);
  transition: width 120ms linear;
}

/* ============================================================
   14. 页脚
   ============================================================ */
.site-footer {
  margin-top: var(--section-y-lg);
  border-top: var(--border-thin) solid var(--color-line);
  background: var(--color-surface);
}

.footer-shell {
  display: grid;
  grid-template-columns: 1.15fr 1.5fr 1.2fr 1.25fr;
  gap: 0;
  padding-top: var(--space-8);
  padding-bottom: var(--space-8);
}

.footer-col {
  padding: 0 var(--space-4);
  border-left: var(--border-thin) solid var(--color-line);
}

.footer-col--brand {
  padding-left: 0;
  border-left: 0;
}

.footer-col:nth-child(2) { padding-top: var(--space-2); }
.footer-col:nth-child(3) { padding-top: var(--space-4); }
.footer-col:nth-child(4) { padding-top: var(--space-6); }

.footer-mark {
  margin: 0 0 var(--space-1);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: 800;
  letter-spacing: -0.01em;
  line-height: 1.15;
}

.footer-tag {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
}

.footer-rule {
  display: block;
  width: 42px;
  height: var(--border-thick);
  margin: var(--space-3) 0;
  background: var(--color-primary);
}

.footer-meta {
  margin: 0;
  max-width: 26ch;
  font-size: var(--text-sm);
  line-height: 1.55;
  color: var(--color-ink-soft);
}

.footer-head {
  margin: 0 0 var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 400;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.footer-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: var(--space-2);
}

.footer-list a {
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  text-decoration: none;
  border-bottom: var(--border-thin) solid transparent;
  transition: color 140ms linear, border-color 140ms linear;
}

.footer-list a:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.footer-list--contact li,
.footer-list--contact span {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  line-height: 1.65;
  letter-spacing: 0.04em;
  color: var(--color-ink-soft);
  word-break: break-word;
}

.footer-base {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.footer-base-shell {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
  padding-top: var(--space-3);
  padding-bottom: var(--space-3);
}

.footer-base p {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-contrast-ink);
}

.footer-geo {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  color: color-mix(in srgb, var(--color-contrast-ink) 62%, transparent);
}

.geo-dot {
  display: inline-block;
  width: 6px;
  height: 6px;
  background: var(--color-contrast-accent);
}

/* ============================================================
   15. 响应式
   ============================================================ */
@media (max-width: 1024px) {
  .grid > .span-3,
  .grid > .span-4,
  .grid > .span-5 { grid-column: span 6; }

  .footer-shell {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: var(--space-6) 0;
  }

  .footer-col:nth-child(3) {
    padding-left: 0;
    padding-top: 0;
    border-left: 0;
  }

  .footer-col:nth-child(4) { padding-top: 0; }
}

@media (max-width: 900px) {
  .header-shell {
    min-height: 70px;
    gap: var(--space-3);
  }

  .header-rule { display: none; }
  .site-nav { margin-left: auto; }
  .nav-toggle { display: inline-flex; }

  .site-nav {
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    display: none;
    background: var(--color-surface);
    border-top: var(--border-thin) solid var(--color-line);
    border-bottom: var(--border-thin) solid var(--color-line);
    padding: var(--space-2) var(--space-4) var(--space-4);
  }

  .site-nav[data-open] { display: block; }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }

  .nav-list a {
    display: block;
    padding: var(--space-3) 0;
    font-size: var(--text-base);
    border-bottom: var(--border-thin) solid var(--color-line);
  }

  .nav-list a[aria-current="page"] {
    border-bottom-color: var(--color-primary);
    color: var(--color-ink);
  }

  .nav-list li:last-child a { border-bottom: 0; }

  .section { margin-top: var(--space-8); }
  .section--lg { margin-top: var(--section-y); }

  .footer-shell {
    grid-template-columns: minmax(0, 1fr);
    gap: var(--space-6);
  }

  .footer-col,
  .footer-col:nth-child(2),
  .footer-col:nth-child(3),
  .footer-col:nth-child(4) {
    padding: 0;
    border-left: 0;
  }
}

@media (max-width: 680px) {
  .grid > .span-3,
  .grid > .span-4,
  .grid > .span-5,
  .grid > .span-6,
  .grid > .span-7,
  .grid > .span-8 { grid-column: span 12; }

  .coord-index {
    padding-left: 0;
    border-left: 0;
  }

  .coord-label { display: none; }

  .sec-head {
    flex-direction: column;
    gap: var(--space-1);
  }
}

@media (max-width: 520px) {
  .coord-index { display: none; }
  .brand-line { display: none; }
  .display { font-size: clamp(44px, 15vw, 72px); }
}

/* ============================================================
   16. 动效偏好
   ============================================================ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}